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07-20-2018, 01:51 AM - 1 Like   #1
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Light polution filter for nocturnal cityscapes - any pointers for WB, PP, etc.?

Hey everyone

For my upcoming Dresden holiday (and cityscapes generally) I've invested in a Rollei Astroklar light pollution filter (reviewed here: Light Pollution, Astroklar & Natural Night Filter Review - Do They Really Work? | Paul Reiffer - Photographer), since I'm looking to do some nighttime long exposures at the Königsufer and possibly other places. The filter should be similar to offerings like NiSi's Natural Night filter, if that broadens the range of relevant user experience?

Rollei themselves recommend adding between 700 and 1,500K to the AWB obtained by the camera without the filter manually, to avoid a cool cast already in camera. Now, I understand that Pentax DSLRs tend to lean towards slightly cooler AWB than major competitors, particularly Canon, yet by default are somewhat conservative in retaining some warmth in tungsten lighting. Would it be wise then to start with moderate AWB correction, say, +700K, or am I trying to be too clever about this? Alternatively, would I get a meaningful AWB with the filter on?

I don't doubt for a second that there will be no substitute for trying and testing this in the field to get some personal bearings, but I bet there will be others on this forum who are using those filters and may have valuable pointers to help me get in the WB ballpark a little sooner?

I'm shooting a K-3 v1.40, will likely be using lenses like the smc DA Limiteds 15 and 35 Macro, and do all my PP in DxO PhotoLab.

07-20-2018, 02:57 AM   #2
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If you're shooting RAW it doesn't really matter, though getting it right may save you a couple of seconds in PP.

Interesting article about the light pollution filters. Thanks for posting.
07-20-2018, 06:13 AM   #3
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Can't hep with the question but thanks for posting the article link!
07-20-2018, 06:29 AM   #4
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First, how well a filter like this will work in a specific part of a specific city depends on the lighting technology used in that particular city. That filter looks especially useful for low-pressure sodium lamps but might not cut as much light pollution created by other kinds of urban lighting.

Second, the filter attenuates both artificial light in the sky and artificial light that's illuminating the cityscape. Thus the filter might give you a nice darker sky but also weird colors on illuminated buildings, people, signs, and vegetation.

Third, thinking about white balance in terms of color temperature is misleading because most modern artificial light sources are not blackbody radiators of some specific cooler or hotter temperature. Moreover, the filter itself modulates the color of every light source (stars, moon, etc.) in complex ways that are not correctable by a simple color temperature shift. Complex white balance shifts are better handled with calibration to a grey card (illuminated by the prevailing artificial light) or calibrating in post with something in the scene that is "white."

Your best strategy is to: shoot RAW so you can manage the white balance in PP; try shooting scene both with and without the filter to check that the filter is helping.

07-20-2018, 07:19 AM   #5
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QuoteOriginally posted by photoptimist Quote
Your best strategy is to: shoot RAW so you can manage the white balance in PP; try shooting scene both with and without the filter to check that the filter is helping.
^^^^^^^^^This

I looked into similar filters and essentially (the one I examined) cuts the low pressure sodium band. However, in my area cities are rapidly removing LPS lamps and replacing with LED's. So I have some concern about how long these filters will continue to be effective. Of course that concern depends on the local area and how fast they are converting to LED (if they are).
07-20-2018, 07:45 AM - 1 Like   #6
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QuoteOriginally posted by jatrax Quote
^^^^^^^^^This

I looked into similar filters and essentially (the one I examined) cuts the low pressure sodium band. However, in my area cities are rapidly removing LPS lamps and replacing with LED's. So I have some concern about how long these filters will continue to be effective. Of course that concern depends on the local area and how fast they are converting to LED (if they are).
A lot depends on LED spectrum. Here is an example of that LED streetlight conversion makes Tucson skies slightly darker, says Dark Sky Association | Local news | tucson.com

I have a simple Hoya Red Intensifier. It definitely cuts out sodium lights skyglow (as most of Light Pollution filters), I even managed to get a bit of Milky Way above the most polluted point (though I have issues stacking it nicely, but it is my problem, not filter problem).


There are some samples No Filter - 1 filter in my Albums.
07-20-2018, 08:45 AM   #7
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These filters sound very interesting, I look forward to seeing your results.

I'd often considered using a graduated ND filter to reduce light pollution, to prevent blown out the ground lighting and with the stars. I'd put the ND filter inverted so the darkest parts are covering the brightest lights, and hopefully the graduated effect would be minimal over the starry skies. Unfortunately, I've been too busy to try it out, and the long hours of light mean I'd have to get up earlier or stay up later than suits my schedule.
07-20-2018, 11:32 AM - 1 Like   #8
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QuoteOriginally posted by Evie Quote
Hoya Red Intensifier
I support this, I believe that other brands call them red enhancing filters. Apparently they offer some pretty good results and their abilities are explored in this article. This subject came up a few months back when someone was wanting to get into astrophotography in this discussion and SSGGeezer suggested them. I had started looking for a light pollution filter and didn't know what to look for so I ended up finding the narrow band filters used by pretty serious astronomers which are silly expensive until I saw the comment from SSGGeezer. this does remind me that I should probably go and get a couple of those red intensifier/enhancer filters for the lenses I use for astro photography.

07-20-2018, 11:38 AM - 1 Like   #9
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QuoteOriginally posted by MossyRocks Quote
I support this, I believe that other brands call them red enhancing filters. Apparently they offer some pretty good results and their abilities are explored in this article. This subject came up a few months back when someone was wanting to get into astrophotography in this discussion and SSGGeezer suggested them. I had started looking for a light pollution filter and didn't know what to look for so I ended up finding the narrow band filters used by pretty serious astronomers which are silly expensive until I saw the comment from SSGGeezer. this does remind me that I should probably go and get a couple of those red intensifier/enhancer filters for the lenses I use for astro photography.
Some time ago I even had a topic with different filters, diameters, prices, reviews - not sure where that topic had gone. Anyway, I found from the same article that Hoya Red Intensifier is one of the cheapest and works almost as well as Pure Night, which quite a bit more expensive. The only negative part - it comes to fixed diameters, so can be used only on matching or close sized lenses. So I bought a specific diameter filter and several rings (up or down). Did not have a chance to try them on normal sky, only on Bortle 8 towards Bortle 9 or so, so cannot comment a lot, but going to Bortle 4 sky where I got reasonably good Milky Way pics, so will see how it will go there. Deciding what lenses to take with me, though...

BTW, Amazon Hoya Red Intensifier comes from Adorama usually, and it is faster to buy from them directly. Would make some better samples, but it says cloudy in my astro weathercast.

Last edited by Evie; 07-20-2018 at 11:44 AM.
07-20-2018, 12:32 PM   #10
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QuoteOriginally posted by Evie Quote
Some time ago I even had a topic with different filters, diameters, prices, reviews - not sure where that topic had gone. Anyway, I found from the same article that Hoya Red Intensifier is one of the cheapest and works almost as well as Pure Night, which quite a bit more expensive. The only negative part - it comes to fixed diameters, so can be used only on matching or close sized lenses. So I bought a specific diameter filter and several rings (up or down). Did not have a chance to try them on normal sky, only on Bortle 8 towards Bortle 9 or so, so cannot comment a lot, but going to Bortle 4 sky where I got reasonably good Milky Way pics, so will see how it will go there. Deciding what lenses to take with me, though...

BTW, Amazon Hoya Red Intensifier comes from Adorama usually, and it is faster to buy from them directly. Would make some better samples, but it says cloudy in my astro weathercast.
Sounds like your skies are similar to mine where I live being in the solid 8 approaching 9 because no one cares about light polluion. The street lamps in my town are those wonderful glass globes that also shine up and there are about 3x as many as are actually needed. Thankfully my lake property is a lower 3 maybe even a high 2 so I do have some good dark sky that I have access to. Some time I will really trek out into the wilderness and go to some 1s but that is really a haul and those places are few and far between.
07-20-2018, 12:49 PM - 1 Like   #11
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QuoteOriginally posted by MossyRocks Quote
Sounds like your skies are similar to mine where I live being in the solid 8 approaching 9 because no one cares about light polluion. The street lamps in my town are those wonderful glass globes that also shine up and there are about 3x as many as are actually needed. Thankfully my lake property is a lower 3 maybe even a high 2 so I do have some good dark sky that I have access to. Some time I will really trek out into the wilderness and go to some 1s but that is really a haul and those places are few and far between.
OK, I am jealous now


I live south of DFW, so MW for me is directly above Dallas, so at best with filter I managed Astrometry.net and Astrometry.net (Astrometry.net) . Unfortunately, I am lacking with editing.... Not comparable with Stitched Milky Way 2015.08.20 - 2015.08.21 ( Evie ) - AstroBin I got without any filters from 4. As I did this with 50mm, I am wondering if to take the same 50mm, or 24 will be enough... (both F1.4, and I am taking other lenses as well).

Though I am jealous of lake property. BTW, I found that Clear Outside v1.0 - International Weather Forecasts For Astronomers also shows a Bortle number of the location, so it is quite useful.
07-20-2018, 02:23 PM   #12
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QuoteOriginally posted by Evie Quote
OK, I am jealous now


I live south of DFW, so MW for me is directly above Dallas, so at best with filter I managed Astrometry.net and Astrometry.net (Astrometry.net) . Unfortunately, I am lacking with editing.... Not comparable with Stitched Milky Way 2015.08.20 - 2015.08.21 ( Evie ) - AstroBin I got without any filters from 4. As I did this with 50mm, I am wondering if to take the same 50mm, or 24 will be enough... (both F1.4, and I am taking other lenses as well).

Though I am jealous of lake property. BTW, I found that Clear Outside v1.0 - International Weather Forecasts For Astronomers also shows a Bortle number of the location, so it is quite useful.
For editing I would almost look for using Deep Sky Stacker (DSS) to do the stitching and stacking. Take a few pictures with the same approximate framing (at least 4 but maybe go higher), then reframe and repeat. Do this until you cover the sky portion that you want. DSS will handle stacking averaging, and aligning the pictures for you. I would say stick with the 50 F1.4 and just double the number of shots but then I have been playing with stitched images a lot lately. You will get more detail. I do like a 50 for taking constellation pictures as most seem to fit in the frame nicely on APS-C. thanks for the weather site, I will have to keep that one around, and it looks like my estimates were pretty close, at high 8 for my home and a low 3 for my lake property. What I really need is for the weather to cooperate some as every time I have could have done some astrophotography it is either been cloudy, or I didn't have my gear (last weekend at cub scout camp).
07-20-2018, 02:34 PM - 1 Like   #13
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QuoteOriginally posted by MossyRocks Quote
For editing I would almost look for using Deep Sky Stacker (DSS) to do the stitching and stacking. Take a few pictures with the same approximate framing (at least 4 but maybe go higher), then reframe and repeat. Do this until you cover the sky portion that you want. DSS will handle stacking averaging, and aligning the pictures for you. I would say stick with the 50 F1.4 and just double the number of shots but then I have been playing with stitched images a lot lately. You will get more detail. I do like a 50 for taking constellation pictures as most seem to fit in the frame nicely on APS-C. thanks for the weather site, I will have to keep that one around, and it looks like my estimates were pretty close, at high 8 for my home and a low 3 for my lake property. What I really need is for the weather to cooperate some as every time I have could have done some astrophotography it is either been cloudy, or I didn't have my gear (last weekend at cub scout camp).
I tried DSS, but definitely was not happy with it. It either did not give me good results, or gave me exceptions. There are lots of settings and they are way too difficult for me, as I am strictly hobyist. Also, the problem in this case was vigneting for different frames in panorama (I cannot darken them one by one, as then the final image is different shaded, and vignetting is not removed good when working with ETTR images)
07-21-2018, 02:43 AM - 1 Like   #14
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Hey, quite a few reactions to my original post. Definitely thanks to everyone for contributing and providing perspectives so far.

Not that much love for and some reservations about the somewhat pricey dedicated light pollution filters, it seems. Suggestions regarding cheaper alternatives such as Hoya's Red Enhancer / Intensifier. And now - admittedly after some googling - I even learnt what the Bortle scale refers to ...

I remain curious, though, what Rollei's Astroklar will actually give me in the field and in post. If anything forum-worthy comes of it, I shall be back with images.
07-22-2018, 02:52 AM   #15
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QuoteOriginally posted by Madaboutpix Quote
Light polution filter
Interesting thread this one, I knew nothing about such things... and still know very little I'll admit.

But as an outsider looking in... I think I'd forego a filter, which appears to further reduce light levels into camera, in what can only be described as, already low or almost no light situations.

Looking at the before and after images posted, I would expect to be able provide that level of correction or even more if required in PP, with most available software packages.

But hey, I could be talking out the back of my behind for all that I know... now how polite was that version.
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